Solar Maximum

Discussion in 'Boat Design' started by JonathanCole, Feb 23, 2010.

  1. Guest625101138

    Guest625101138 Previous Member

    It is amazing how readily many accept what currently exists but few have little imagination with new concepts.

    Imagine if you had only ever used motor boats and someone came along with a sailing boat. You would wonder what on earth all the cloth was for. Huge areas of white fabric - how ridiculous.

    Solar arrays have huge potential for long range cruising. They will harvest about 30W/kg of panel. In tropical latitudes that will work out to be about 180Wh/kg/day.

    Diesel will produce about 5kWh/kg. A little maths shows that if you are planning long range cruising in excess of 30 days or more the solar panels come as the best option in terms of reducing boat weight. It gets less attractive for solar alone in cooler parts but then wind turbines become attractive.

    The technology is already capable. It will become more convincing as more boats choose to use solar.
  2. kach22i
    Joined: Feb 2005
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    kach22i Architect

    So very true.
  3. Boston

    Boston Previous Member

    three cheers for actually building it
  4. creosote
    Joined: Dec 2010
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    creosote Junior Member


    True, but the sail could be made into a reflector and concentrate the solar energy at a focus.

    The sail would not naturally form a parabola in line with the sun, but shaping a sail and coating it with a mylar like produce must be easier than making it out of PV cells.
  5. creosote
    Joined: Dec 2010
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    creosote Junior Member

    Oops, sails are already being made with mylar.
    (obviously I'm not into sail boats.)

    So the next step is to apply the metal coating for reflection purposes, (which should be easy) then put something at the focus to collect the solar energy, which won't work if you're sailing into the sun.

    The solar collector can be either PV cells, or a black box to collect the heat and drive a sterling engine.

    Before I get carried away with calculating the curves of a sail and determining the focus, I should point out that in Spain, they tried a similar project to make electricity and failed to break even.
  6. CDK
    Joined: Aug 2007
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    CDK retired engineer

    You are getting carried away already.

    To focus solar radiation you must control the angle of incidence, so a sailing vessel is unsuitable.

    The setup in Andalusia, Spain was a research project to demonstrate how concentrated radiation can generate electricity using steam as a medium. It was built long ago, when crude oil was just a few $$ a barrel, so the high initial cost for this large plant made the generated electricity pretty expensive. With today's $ 92.60 a barrel the break even point is a quite different one.

    Commercial exploitation is feasible now, but like all solar power plants, it generates energy on an intermittent basis only, with peak output when demand is minimal.
  7. Bruce46
    Joined: Jul 2006
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    Bruce46 Junior Member

    How about a boat that looks like an old Elco flattop with solar panels and batteries for rainy days?
  8. Chickadee
    Joined: Jul 2005
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    Chickadee Junior Member

    Solar boat across the Atlantic

    Seems PlanetSolar had to add some laterals panels? see attachment. They are now in Carthagena!

    I understand they crossed the Atlantic in 26 days, 3,5 knots? That would not be really impressive, just a little better than the Sun21 in 2007, 29 days... but this one was much smaller, see their website for some technical data: Sun21

    FUnny to see that both are swiss projects!

    Attached Files:

  9. Boston

    Boston Previous Member

    I've crunched those numbers a thousand times and its just not practical. see old wind turbines are easy to make

    You end up using "tons" of batteries and it takes forever to charge them. you could spend more for lithium Ion batteries and save some weight space and time charging but the cost is prohibitive and not likely to drop anytime soon what with China controlling the rare earth minerals market and withholding the supply.

    the solar panels need to get lighter and provide greater energy density than ~12 watts sq/ft and even at that a 280 watt panel still costs ~$800 each. Wind generators might be a more practical approach for a small yacht but thats a whole other can of worms.

    its pretty much a mater of stored wattage and how slow your willing to go.

    best of luck
  10. mark775

    mark775 Guest

    Bos, I don't know anything about the politics of this. "withholding the supply" - Is this happening?
  11. Boston

    Boston Previous Member

    sure is
    I"ll try and dig up the article for you


    Over the last few years they bought as many rare earth mines as they could and shipped the product off to China for batteries and plasma monitors and such. Now it looks like they are moving towards decreasing exports of the raw material and increasing the price. Can you say monopoly. My fave part is this lunatic idea of "free" trade is about to have its bubble burst.
  12. Prospector
    Joined: Dec 2010
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    Prospector New Member

    Turanor Planet Solar

    Hello, great design, the only thing lacking are the mast and sails. It does look good on the water. Last known whereabouts : Miami, Fl. USA.
    Check out Marine
    I was glad to see some pics of construction,
    Thanks Prospector
  13. yipster
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    yipster designer

  14. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Again, besides all the inefficiencies with solar panels you have these critical problems.
    1. The larger the boat, the more solar panels, but then you need more power to power the boat.
    2. At best you only get full power for only a couple of hours a day, unless you mount panels on a rotating assembly which is very hard to do on a boat.
    3. Any shading will cut power production drastically.
    4. When you convert solar DC voltage to actual hp on the shaft, what you get is a joke of only like 5 or 10 hp. What you get is a boat that drifts in the current more than it powers through anything.

    Put a sail on the damn boat and you can travel around the world for free...

  15. Tad
    Joined: Mar 2002
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    Tad Boat Designer

    PlanetSolar took 584 days to get round, Banque Populaire V did it in 45.5 days and I'll guess at lower cost. If it's slower and costs more where is the advantage? Miss-directed technology?
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